Inorganic Surface Engineering to Enhance Perovskite Solar Cell Efficiency.

The photoconversion efficiency of perovskite solar cells (PSCs) is enhanced by the deposition of inorganic nanoparticles (NPs) at the interface between the compact TiO2 electron-selective contact and the mesoporous TiO2 film. The NPs used are core/shell Au@SiO2, where a thin SiO2 coating protects the Au core from the direct chemical interaction with CH3NH3PbI3 halide perovskite used as light-harvesting material. The samples prepared with Au@SiO2 NPs exhibit a higher external quantum efficiency in the complete wavelength range at which perovskite presents light absorption and not just at the wavelengths at which Au@SiO2 NPs present their absorption peak. This fact rules out a direct plasmonic process as responsible for the enhancement of cell performance. A detailed characterization by photoluminescence, impedance spectroscopy, and open-circuit voltage decay unveils a modification of the interfacial properties with an augmentation of the interfacial electrostatic potential that increases both photovoltage and photocurrent. This article highlights the dramatic role of interfaces in the performance of PSCs. The use of reduced quantities of highly stable inorganic compounds to modify the PSC interface instead of the extensively used organic compounds opens the door to a new surface engineering based on inorganic compounds.